This invention relates to stethoscopes utilized in medical diagnosis and more particularly it relates to a novel stethoscope having a new stethoscope chest piece, which has characteristics greatly improved over the characteristics of stethoscopes known heretofore, and having a sound mixer. This invention specifically relates to a further improved stethoscope having improved characteristics over those found in my previous stethoscope chestpiece invention as described in U.S. Pat. No. 3,067,833, issued to me. The user of the invention can, at his option, employ a sound mixing block which when used in conjunction with the improved stethoscope chest piece provides the most greatly improved characteristics over those found in stethoscopes known heretofore. For his investigation of a variety of normal and abnormal sounds produced within the human body, the physician relies in large measure upon listening to these sounds with a stethoscope. Of particular importance are the characteristics of the heart sounds, heart murmurs, breath sounds and rales. The presence of any one of several types of lesions in or near the valves of the heart give rise to eddies in the blood flow. Such eddies result in abnormal sounds known as murmurs. Murmurs are important in the diagnosis of several conditions such as mitral stenosis, which is a narrowing of the left atrioventricular orifice. Rales are those sounds produced by the passage of air through portions of the bronchial tree which have been narrowed or which contain fluid and debris.
All the aforementioned sounds consist of mixtures of tones of different frequencies and intensities. Each sound consists of the fundamental tone, which is the note of lowest pitch, and a number of higher-pitched tones called the overtones. The tonal quality of a sound is determined by the number of overtones present, the frequencies of the overtones and their relative intensities. Generally, the more overtones present, the richer the tone color or tone quality. To reproduce sound faithfully, an instrument must be capable of transmitting all frequencies involved and must transmit them at an adequate intensity.
It is well known that the standard stethoscope does not transmit all sound frequencies and that it cannot amplify sound. Therefore it cannot transmit all overtones and cannot faithfully reproduce the sounds which come from the heart and lungs in all their natural color. Additionally, the standard stethoscope does not generally provide for the stereophonic transmission of two separate sounds from the sound chamber. The usual practice is to transmit the sound coming from the sound chamber through a single tube for a distance of about two feet. After that distance has been traversed, the tube is split at a "Y" joint with the two separate tubes each carrying the sounds of one of the stethoscope user's ears. Such non-stereophonic or monaural sound transmission provides the same sound of each of the physician's ears; this does not provide for an optimum transmission of the sound of interest. For these reasons, the conventional stethoscope has fallen into disrepute as a diagnostic instrument for discerning pathologic changes in body structures.
When a sound is initiated in a large empty room, the persistence of that sound is most striking; this phenomenon being that of reverberation and being caused by multiple echo reflections repeated in rapid succession within a closed space in which there is little absorption of sound energy. In the conventional diaphragm-type chest piece, just such a closed space exists as a sound chamber in which sound waves initiated by diaphragmatic excursion travel to the walls of the sound chamber and are reflected back and forth at random. Because the surfaces of the sound chamber are polished and hard and non-porous, absorption of sound is poor, and sound energy tends to build up as reverberation. Reverberation also tends to be more extensive in smaller chambers because reflections follow one another more rapidly. Reverberation time in the ordinary chest piece tends to be high, and as a result there is confusion between tones being perceived by the stethoscope user and the echo reflections of the preceding tones that the stethoscope user has already heard. Moreover, muddling, indistinctness and lack of intelligibility of the sounds are additional problems present in the conventional stethoscope.
My earlier improved stethoscope, as described in U.S. Pat. No. 3,067,833, had improved sound reception and transmission characteristics. These improved sound reception and transmission characteristics, via the diaphragm enclosed chamber of my invention described in U.S. Pat. No. 3,067,833, were particularly an improvement in the sound range from approximately 90 to 2,000 cycles per second (CPS).
The present invention utilizes a portion of the structure of my previous invention and also incorporates a new, second sound chamber. The new, second sound chamber used in my present invention has improved sound reception and transmission characteristics, particularly in the range of approximately 20 to 90 CPS. Accordingly, the present invention, by utilizing two optionally selected and optionally acoustically interconnected sound chambers, provides a stethoscope having improved sound reception and transmission characteristics for sounds occuring in the range of approximately 20 to 2,000 CPS.
The present invention in one of its embodiments also provides for separate stereophonic transmission of sound from the sound chamber to each of the stethoscope user's ears, thus overcoming the mixed sound characteristics of previous stethoscopes which transmitted the same sound via a single tube, with a "Y" shaped split, to the stethoscope user's two ears. The present invention in another of its embodiments further provides for transmission of two slightly different acoustic images, one to each of the stethoscope user's ears, thus creating a stereophonic effect. This is in contrast to the ordinary stethoscope which transmits only one acoustic image, via a single tube with a "Y" shaped split to the two ears of the stethoscope user.
In yet another embodiment of the present invention there is provided a sound mixing block which is optionally useable with either of the improved stethoscope chestpieces of the present invention. When the sound mixing block is used, the stethoscope user receives the richest and most intense sounds from the patient.
It is therefore an object of this invention of provide an improved stethoscope utilizing an improved stethoscope chestpiece which is capable of intensifying sound.
It is another object of this invention to provide such a chest piece which will increase the distinctiveness of a plurality of different sounds.
It is another object of this invention to provide such a chest piece which will provide increased resolution and clarity of the transmitted sounds.
It is another object of this invention to provide such a chest piece which is capable of faithfully transmitting sound having an extremely broad range of frequencies.
It is another object of this invention to provide such a chest piece which has two sound chambers.
It is another object of this invention to provide such a chest piece which has one sound chamber designed for excellent reception and transmission of sounds in the 20 to 90 CPS range and a second sound chamber designed for excellent reception and transmission of sounds in the 90 to 2,000 CPS range.
It is yet another object of this invention to provide such a chest piece, incorporating all of the objects recited above, which further provides a facility for a stereophonic transmission of sounds from the sound chambers of the chest piece to the stethoscope user's two ears via two separate sound transmission tubes.
It is yet another object of this invention to provide a chest piece, incorporating all of the objects recited above, wherein the two sound chambers are optionally selectable and wherein acoustic connection or insulation of the two sound chambers, one to another, is optionally selectable.
It is another object of this invention to provide a sound mixing apparatus which permits a portion of the sounds traveling through two separate passageways leading from a stethoscope chest piece to the stethoscope user's ears to be mixed together thus providing an increased stereophonic effect and improving the depth of the sound perceived by the stethoscope user.
It is another object of this invention to accomplish the object set forth immediately above wherein the sound mixing apparatus is optionally useable by the stethoscope user.
Other objects and advantages of this invention will be apparent to those of ordinary skill in the art from the following specification and brief description of the drawings.